MicroRNAs (miRNAs) must be processed in order to mature and successfully bind to target mRNAs to exert translational repression and/or mRNA degradation. Through the canonical miRNA biogenesis pathway, miRNAs are transcribed from intergenic or intronic loci by RNA polymerase II. The resulting primary miRNAs are then processed by the Microprocessor, an enzyme complex that consists of Drosha, a catalytic RNase III enzyme, and a homodimer of the RNA-binding protein DGCR8 (known as PASH-1 in C. elegans) to produce a precursor miRNA. Subsequent processing by Dicer, another catalytic RNase III enzyme, produces the miRNA that is loaded into Argonaute to regulate gene expression. However, there are many noncanonical pathways that bypass one or more steps in the canonical processing pathway. Notably, the biogenesis of mirtrons bypasses Microprocessor cleavage and instead relies on mRNA splicing. In this Microprocessor-independent pathway, splicing of small introns generates miRNA precursors suitable for Dicer processing. Recent data from our lab using a temperature-sensitive allele of
pash-1 in C. elegans revealed a unique family of PASH-1-independent miRNAs, the
mir-1829 family. The
mir-1829 family is derived from unusually long introns (ranging from 844-1861 nucleotides in length) of three host genes that have no apparent overlapping functions. We aim to characterize the biogenesis of the
mir-1829 family in C. elegans, first determining whether they require Dicer for maturation and if they are splicing-dependent. We will also examine if they function in repression and play a role in physiology. Thus far, we have generated multiple mutant strains with various combinations of
mir-1829 family members deleted to determine if they display any mutant phenotype. Understanding the biogenesis and function of the
mir-1829 family will provide further insight into noncanonical miRNA processing pathways and the biology of miRNAs.